Switch



Feb. 27, 1951 R. E mouw 2,543,707

SWITCH 2 Sheets-Sheet 1 Original Filed Oct. 31, 1947 R. E. PROUTY Feb.27, 1951 SWITCH 2 Shqets-Sheet 2 original 1mm oet. :51,` 1947 QNl@Patented Feb. 21, 1951 2,543,707

UNITED sTATEs PATENT oFFlcE L Robert E. Prouty, Logansport, Ind.,assignor to Essex Wire Corporation, Loganaport, Ind., a corporation oiMichigan Original application October 31,4947, Serial No.

1949, Serial No. 102,907

(Cl. 20o-122) 6 Claims.

My invention relates, generally, to electric cirfor use in protectingfractional horsepower motors 5 Referring now particularly to Figures 1through from becoming overloaded and can be used in 4 of the drawings,it will be observed that the conjunction with the series type ofstarting relay reference character I designates, generally, a disclosedin my copending application, Serial No. thermal overload protectordevice constructed in 783,410, flied October 3l, 1947 and assigned tothe accordance with my invention. The device Il assignee of thisapplication. l0 includes a housing or case II of insulating mate- Thisis a divisional application of my copending application Serial No.'183.411, illed Octobe 31, 1947.

Among the objects of my invention are: To provide a mount for springsused in conjunction with a switch of a character that will permitadjustment of the biasing forces exerted thereby;

to provide a resilient bracket for mounting each spring with the portionanchored tothe spring adjustable relative to the remaining portion; toemploy a bimetallic spring strip as one of the springs and to use anelectric heater element for heating the same to operate the switchcontact; and to employ normally closed contacts connected in series withthe heater element so that the device can function to protect'electrical apparatus, such as a motor from overloads.

Other objects of my invention will, in part, be obvious and in partappear hereinafter.

My invention is disclosed in the embodiment thereof shown in theaccompanying drawings and it comprises the features of construction,combination of elements and arrangement of parts which will beexemplined in the construction hereinafter set forth and the scope ofthe application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of myinvention, reference can be had to the following detailed description,taken together with the accompanying drawings, in which:

Figure 1 is a detail sectional view taken along the line I-I of Figure 2and showing, in elevation, certain of the parts making up the overloadprotector switch of my invention;

Figure 2 is a detail sectional view taken along the line 2-2 of Figurel;

Figure 3 is a detail sectional view taken along the lines 2-3 of Figurel;

Figure 4 is a perspective view of the parts making up the overloadprotector switch shown in disassembled relation; and

Figure 5 illustrates, diagrammatically, how the overload protectorswitch of my invention can be Divided and this application July 2.

employed in conjunction with the motor starting relay disclosed in mycopending application above referred to for protecting a split phasefractional horsepower motor from overloads.'

rial such as a phenolic condensation product. It has integrally formedfoot portions I2 and a cover Il, formed of the same material as the caseI I, and secured to the foot portions I2 by hollow rivets or eyelets I4.Screw terminals I5 and I6 are provided on the upper side of the case Ilto permit external connection to the mechanism located inside.

Within the case or housing II there is positioned a support of suitableinsulating material such as a phenolic condensation product whichprovides the framework upon which the thermal overload mechanism ismounted. Secured by a tubular rivet I8, Figure 4, to the support Il is aconductor strip I9 which carries a stationary contact in the form of asilver button. A lead 2i is soldered to the tubular rivet I8 and to thescrew terminal I6 to interconnect them. The stationary contact 20 isarranged to be engaged by a movable contact 24, also in the form of asilver button, that is carried by a leaf spring formed of suitableresilient and conducting material such as beryllium copper. While theleaf spring 25 is shown as being formed of a single strip of narrow flatmaterial, it will be understood'that it can be formed so as to provide agenerally rectangular shape vas disclosed in my copending applicationabove referred to.

The manner in which the spring 25 is adjustably mounted on the supportI1 constitutes an importantfeature of my invention. It will be observedthat the left hand end of the spring 25, as viewed in Figure 4, issecured by rivets 26 to an arm 21 of a U-shaped elongated bracket 28formed of resilient material such as brass. In this manner the spring 25is anchored in cantilever fashion to the U-shaped bracket 28. Theopposite arm of the U-shaped bracket 28 includes apertured ears 29 whichare fastened solidly to the adjacent side of the support I1 by a rivet30 and a sleeve 3|. The rivet 30 and sleeve 2i project through thesupport I1 and serve to hold another bracket similar to the bracket 28in position on the opposite side as will be described hereinafter. Witha view to adiusting the biasing ausge? force exerted by the spring 25,an adjusting screw 32 is threaded through the juxtaposed portions of thespring 25 and the arm 21. Its inner end bears against the adjacent sideof the support i1. By turning the screw 32 in or out, the arms oi theU-shaped bracket 29 are correspondingly moved resulting in acorresponding stressing of the spring 25.

Another important feature of my invention resides in the provision ofmeans for moving the spring 25 to separate the contacts 20 and 24 whichnormally are in the closed or engaged position. It will be understood,however, that the construction may be such that the' contacts 2|) and 24are normally in the open position. Since the device i is employed as athermal overload protector. the contacts 2U and 24 normally are closedto complete the circuit therethrough which circuit isopened only in theevent that the overload conditions exist for the required time to effectthe separation of the contacts and 24.

The mechanism for moving the spring to separate the contacts 20 and 24includes an actuator 34 in the form of a short rod of nonmagneticmaterial such as aluminum. 'I'he actuator 34 is arranged to moverelative to a permanent magnet 35 which is generally rectangular inshape and has a generally I-shaped cross section. The ends of theI-shaped permanent magnet 35 provide poles 36 and 31 having fiat sideswhich are parallel to each other. The ends forming the poles 39 and 31are interconnected by an intermediate section 3B which has an aperture39 through which the actuator 34 is movable. At the ends of the actuator34 stop members 40 and 4| are provided in the form of circular washers.They are held to the ends of the actuator 34 by cap nuts 42. Asindicated in Figure 4 the stop members 40 and 4| are formed of magneticor non-magnetic material depending upon the particular application ofthe magnetic control mechanism. Thus three combinations of magneticmembers are possible in that the stop member 40 may be of non-magneticmaterial and the stop member 4| of magnetic material or the stop member40 may be of magnetic material and the stop member 4| may be ofnon-magnetic material.

Finally, both members 40 and 4| may be formed of magnetic material. Snapaction in the operation of the contacts 2D and 24 is provided by thecooperation between the permanent magnet 35 and the stop members y4|!and 4| when they are formed of magnetic material.

The permanent magnet 35 is positioned in a generally rectangular opening43 in the support |1. It is held securely in place on the support l1 ,byplates 44 which are secured to the support |1 is a duplicate of bracket28 previously described.

The bimetellic spring strip 43 is acted upon by heat generated by aheater element Il which has terminals 53 and I1. The terminal 53 issecured to one end of the sleeve 3| while the terminal 41 may be securedto one end of the sleeve 43. It can be otherwise mounted es describedhereinafter. It will be apparent that the heater element ll is connectedin series circuit relation with the normally closed contacts 2l and 24through the sleeve 3|.

The thermal overload protector device il, less the case and cover I3,may be mounted on the frame of the electromagnetic relay disclosed in mycopending application above referred to. In order to facilitate suchmounting the support |1 is provided with an additional aperture Il,Figure 4, for registering with a corresponding aperture in the trame ofthe electromagnetic relay to receive a holding rivet.

Referring now particularly to the diagram shown in Figure 5, it will beobserved that reference character 93 designates. generally, a splitphase fractional horsepower motor. such as employed for operating arefrigerator. having a squirrel cage rotor 3| and start and run windings32 and 63. A relay winding 34, such as the winding of the relaydisclosed in my copending application referred to above, is connectedin' series circuit relation with the run winding 33 for controlling theoperation of starting contacts 35 and 33 which are connected in serieswith the start winding 82. Line terminals 31 and 33 are employed forconnecting the motor 3l to a suitable source of current such as a 60cycle 110 volt source. It will be noted that the energizing circuit forthe motor 3l extends from the line terminal 31 through heater element55, spring 2l, contacts 24 and 2l, relay winding 34, start winding 33 toline terminal 63. When the terminals 31 and 88 are energized from asuitable source of alternating current, sufiicient current hows throughthe circuit just traced to cause the relay winding 64 to close startingcontacts 35 and 33. Start winding 32 is thereupon energized and therotor 6| is brought up to speed. The current iiow through the relaywinding 34 then drops suficiently to permit the contacts 35 and I3 toopen. Thereafter the motor 3l continues to operate with only its runwinding 53 energized.

In the event that the motor 30 should not start.

or in the event that it should become overloaded in operation, sumcientcurrent ilows through the heater element 55 for a suiiicient time tocause the bimetallic spring strip 43 to expand and move f the actuator34 to the right, as viewed in Figure 5, for opening the contacts 23 and24. The previously traced energizing circuit for the motor 33 is openedand further damage to the motor Il is prevented. At the same timecurrent owing through the heater element 55 is interrupted and thebimetallic spring strip 49 cools and returns to its initial position.

The contacts 20 and 24 may be closed automatically on return of thebimetallic spring strip 49 to its initial position or they may be heldin the open position depending upon the biasing action exerted by thespring 25 and the material of which the stop members 40 and 4| are made.If it is desired that the contacts 2|I and 24 automatically reclose, thestop members 43 is formed of nonmagnetic material and the stop member 4|is formed of magnetic material. This arrangement provides a time delayin the operation o! the actuator 34 by the bimetallic spring strip 49.However, -when sufilcient force is applied to the actuator $4 by thebimetallic spring strip ll, the

lower end in contacting engagement with stop member 4| of magneticmaterial is separated from the permanent magnet 3l and the spring 25 isengaged with a snap action to eifect a cor-` responding rapid separationof the contacts and 2l. As soon as the heater element -55 cools down,the bimetallic spring strip I9 returns to its initial position and thebiasing action of the spring 2B is sumcient together with the magneticattraction between the permanent magnet I5 and the stop member 4I ofmagnetic material to move the actuator 34 to the left, therebypermitting the contacts 2li and 24 to be closed with a snap action. c

In the event that it is desired that the contacts 20 and 2l be held inthe open position, the stop member lll is formed 'of magnetic materialand the stop member 4| is formed of non-magnetic material. In this case,once the actuator u has been operated so that the stop member 4I ofmagnetic material is moved into engagement with the poles 36 and 31 ofthe permanent magnet 35, the actuator 34 is heldl in this position afterthe heater element 56 cools down and the bimetallic spring strip 49 isrestored to its initial position. The contacts 20 and 24 then can bemanually reclosed as described in more detail in my copend-` ingapplication Serial No. 783,412, filed October 3l, 1947.

If it is desired to provide additional time delay in the movement of theactuator 3l then the stop member l0 is formed of magnetic material, theother stop member Il also can be formed of magnetic material. Also byproper adjustment of the biasing forces exerted by the spring and thebimetallic spring strip 49 variations in the operating characteristicsof the device l0 can be obtained. 'I'liese adjustments together withproper selection of the material of which the stop members I0 and Il aremade provide a wide range in the operating characteristics of the devicein as will be understood readily.

If desired, instead of securing the terminal 51 of the heater element 55to the sleeve I6, it may be secured to a sleeve 69, as shown in Figure2, which projects through an aperture 10, Figure 4, in the support i1and is held thereto by having one end spun over like a hollow rivet. Insuch case the sleeve 4B would be omitted and a rivet, similar to therivet 45. employed in its stead. A lead 1i may be provided tointerconnect the sleeve i9 and the screw terminal l5.

Since further changes can be made in the foregoihg construction anddifferent embodiments of my invention can be made without departing fromthe spirit and scope thereof, it is intended that all matter shown inthe accompanying drawings, and described hereinbefore y shall beinterpreted as illustrative and not inta limiting sense.

I claim as my invention:

l. In a switch, in combination, a support, an elongated bracket fastenedat its ends to said support and having an intermediate upper sectionspaced from said support and fastened thereto by means of spaced-apart,offset, lower mounting ears flanking either end of'said intermediatesection, a bimetallic spring strip anchored at one end to saidintermediate section, a pair of relatively movable contacts one of whichoperates with the other end'of said bimetallic spring strip formovementrelative to the other contact, an element for applying heat tosaid bimetallic strip for operating said contacts, and means threadedthrough said intermediate section and having its said support forchanging the position of said intermediate section relative to saidsupport to adjust the biasing action of said bimetallic spring strip.A

2. In a switch, in combination, a support, an elongated bracket fastenedat its ends to said support and having an intermediate section spacedfrom said support and a pair of anking, lower, otlset mounting ears, anelongated spring anchored at one end to said intermediate section,

a pair o f separable contacts, one of said contacts cooperating with theother end of said spring for movement relative to the other contactmounted on said support, and means extending through said intermediatesection and having its lower end in surface contacting engagementwithsaid support for changing the position of said intermediate sectionrelative to said support to adjust the biasing action of said spring.

3. In a thermal device of the class described, a single wall support, apair of resilient elongated brackets mounted transversely at one end ofsaid support, but on opposite sides thereof, said brackets each beingcharacterized by an upper mounting arm normally spaced parallel to saidsupport in its mounted position therewith, a pair of spaced ears belowsaid arm adapted for mount-- ing said bracket to said support, and awall member fashioned at right angles to said spaced ears forinterconnecting said upper arm with said lower ears; a resilient leafmember mounted to each of said bracket upper arms so as to extend inspaced cantilever relation over said support, and adjusting meansassociated with each of said brackets, extending through an associatedupper arm and contacting the surface of said support for independentlytilting each of said upper arms about an axis parallel to said support.

4. In a thermally responsive device of the class described, a singleWall support, an adjusting bracket mounted at one end of said support,said bracket being distinguished by a pair of separated lower mountingears integrally formed with an interconnecting wall and an upper armwhich is spaced from said support, a resilient leaf spring mounted incantilever fashion to said upper arm so as to extend over said support,and an adjusting screw, threaded through said spring and upper arm,having its lower end in surface contact with said support whereby saidspring may be moved arcuately about said bracket relative to saidsupport.

5. In an adjusting bracket for mounting a leaf member in cantileverfashion over a support member, a resilient upper mounting arm forsupporting said leaf member in cantilever fashion, a pair of spacedapart lower mounting ears for mounting said bracket to said support, arigid wall member interconnecting said ear members and said upper armwhereby said ears and arm are normally positioned in spaced parallelrelation, and an adjusting threaded member inserted through said leafmember and said upper arm adapted to contact the surface of said supportbetween said ear members wherebysaid upper arm and leaf member may beadjustably rotated about an axis parallel to said support.

formed integrally with said wall and positioned in spaced parallelrelation with said two ears, the lateral extremities of said upper armlying within the space between said two ears, but thereabove; and anadjusting threaded member mounted through said upper arm and said leafmember which is mountable thereon, the lower end of said threaded membercontacting said support, between said spaced ears, and said threadedmember being adapted for threading adjustable movement along an axisnormal to said support whereby said upper arm and attached leaf may beangularly tilted relative to said bracket wall and said support.v

ROBERT E. POUTY.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS

